Revert "Add optimized version of memcpy for Cortex A9"

 * Too many weird regressions in this codepath.

This reverts commit 8c35d7eaeb67ace9a96922f16ba9e491dcde6534.
libc: Enable the fast memmove for NEON targets

 * The CodeAurora version of memmove provides roughly 20x the throughput
   of the default version for all tested platforms. Enable it.

Change-Id: Ia9740f6b38a72c0bd6a6818c96d73e2c23bb5979
libc: Add optimized memcpy for Cortex-A15

 * This version is from Newlib and is written/recommended by ARM as the best
   routine for Cortex-A15.

Change-Id: Ie9c2817dabda929ae4efaada5f6d467d53551ba4